1. Field of the Invention
The present invention relates to a ball joint for use in various industrial appliances, in particular, for use in a cable guide.
2. Description of the Related Art
Conventionally, a ball joint for a cable guide is structured as shown in FIG. 4. Reference numeral 1 designates a ball joint and 2 designates a cable. The ball joint 1 is interposed between a cable fixation table 3 for fixing one end of the cable and a cable supporting table 4 for supporting an intermediate portion of the cable and changing the drawn out direction approximately at 90 degrees. The ball joint 1 comprises a U-letter shaped retainer 5, a shaft 6 bridged between a pair of legs 5a of U-letter shaped retainer, a cubic body 7 coupled rotatably with the shaft 6 and an outer ring 8 to be coupled with the cubic surface of the cubic body 7. The retainer 5 is mounted on a mounting plate 9 with a bolt 10 connected to the bottom of the leg portions 3a of the cable fixation table 3 with bolt 9. The outer ring 8 is mounted on one end 4a of the supporting table 4 with bolt 11.
In operation, the cable 2 is drawn downward approximately vertically from the cable fixation table 3, then wound two or three times in loop on the cable supporting table 4, and further drawn out in an approximately horizontal direction through a ring guide 12 on the cable supporting table 4. In the above mentioned ball joint 1, the cubic body 7 rotates against shaft 6 and the outer ring 8 also rotates against the cubic body 7, so that the cable supporting table 4 can swing three-dimensionally, which guarantees the cable 2 is able to move freely.
According to the above mentioned cable guide system, if the cable 2 is not wound in a loop on the cable supporting table 4, it is swung excessively. An inordinate tension is put on the cable 2, or the cable 2 is forced to be bent at a sharp angle. Therefore, it has become unavoidable to wind the cable in a loop on the supporting table 4.
However, there is a problem where the cable 2 is wound in a loop on the cable supporting table 4, and the cable supporting table 4 is swinging. The cable 2 is apt to be damaged due to frictional contact between the cable and the cable supporting table. In addition, due to the three-dimensional swinging of the cable supporting table 4, the cable 2 is apt to be twisted at the looped portion, so that a lead in the cable can be broken.